The present invention concerns the field of digital communication and pertains particularly to efficient generation within a remote base station of a synchronization signal for a cordless communication system.
A cordless telephone system generally includes a fixed part, which connects a telephone network to one or more base stations. Base stations are generally connected to a fixed part by wires, or may be integrated directly with the fixed part. For example, a system may include a master base station and several remote base stations connected by a wire highway to the master base station. Each base station communicates with one or more portable parts, typically a handset, via a radio frequency (RF) signal link. For example, the cordless system may be included in a private branch exchange (PBX) and utilize a cordless telephone system in accordance with the Digital European Cordless Telecommunications (DECT) Common Interface.
For example, the base stations may be connected together using an data highway operating in accordance with a voice coding algorithm such as an Adaptive Pulse Code Modulation (ADPCM) highway. An ADPCM highway utilizes four wires to connect the base stations. For each base station, one wire carries a synchronization signal (ADPCM.FS), one wire carries a clock signal (ADPCM.CLK), one wire carries data in to the base station (ADPCM.DIP) and one wire carries data out from the base station (ADPCM.DOP).
When a system includes more than one base station which utilize the DECT common interface, each base station must transmit messages in synchronization with a system wide DECT frame synchronization signal. In order to assure proper synchronization, the DECT frame synchronization signal is forwarded by a master source to each remote base station over a dedicated wire.